Grounding in an old house

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  #1  
Old 08-19-07, 02:28 PM
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Grounding in an old house

I just moved into a condo with original 1952 wiring. All of the receptacles but one were 2 prong polarized. I got one of those cheap outlet testers and tested the sole 3-prong outlet, and it detected a good ground. However, after removing the cover, I noticed that there was nothing hooked up to the grounding terminal of the outlet. I'm guessing that the metal wall box is grounded, and the outlet is getting its ground from being screwed into this.

Is this safe? I'm almost certain that this was never allowed in the electrical code.
 
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Old 08-19-07, 04:23 PM
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You could be guessing wrong. Depends on the scale($$$) of the house. In '52, upscale houses had wires with a ground conductor, cheaper houses did not. Even those with a ground, had the ground wrapped around the cable and clamped to the electrical box. It may or may not have been connected continuously back to the service panel, but the connection at the box was generally reliable, at the time.
Installing a 3 prong outlet to this wiring does not conform to current code and is not allowed, although there may(??) be a ground. Not sure what you are looking for. if you need a computer quality ground connection, it is unlikely you will find one. For general purpose electrical appliances, there should be no problems. Any appliance with a third(ground) projection plug will fit a grounded outlet, but there may be no ground connection.
Hope this helps.
 
  #3  
Old 08-19-07, 07:55 PM
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Just curious, do you have romex type "cable" coming into your box or are they individual wires ran inside conduit. If you have metal conduit then the metal conduit serves as the ground. It would or rather should have a continous path back to the main panel's Neutral/ground bar. Metal conduit is (so I hear) not always so reliable as a ground, as weak areas of connection of the conduit can occur over time. I am just a novice but this is what I read (I think LOL) Also I believe I once seen a very small gauge ground wire that did not enter the box with the cable , or rather entered and immediately exited and was fastened to the outside of the metal box somehow. Could be a false memory though. The pro's will be by shortly I'm sure.
 
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Old 08-20-07, 08:31 PM
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I do have a good connection back to the neutral box. I tested it with an Ohm meter. I'm almost certain that it's the metal conduit that is carrying it like sidecutter suggested. I was unable to find any wires other than the hot an neutral. All of the boxes show continuity between the box and neutral. It sounds like I would have to run a ground wire if I want to add more 3-prong outlets though. Guess it's time to call the electrician. I'll probably get them to sink a grounding rod while they are here too, since the current setup is through the cold water pipes.

Thanks for advice, all.
 
  #5  
Old 08-20-07, 08:58 PM
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If indeed you have a "legitimate" ground via the metal conduit ( the question is "legitimate") then I would think you could replace your receptacles with 3-prong receptacles, using what they call self-grounding receptacles (available at HD for about 98 cents apiece). I am a novice so please don't do this until a seasoned electrician "confirms". Your other option which is well known is to find (if you know how to do it) the first receptacle of each branch circuit and install a GFI receptacle there. If you wire it in what they call Line/Load then the remaining receptacles on that branch circuit can indeed be replaced with 3 prong receptacles. There's some "stickers" (forgot what I read they say) that you have to make visible at each receptacle location saying something to the effect that this is not a "true grounded receptacle" , only GFI protected. The sticker would be required only " I think" if indeed you don't have a legitimate ground. Grounding rods I am not yet qualified to speak to much about with absolute certainty.
 
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